A dye having been well-known as a dyestuff or a pigment has widely been utilized in various applications such as a dyestuff for textile, a colorant for resin or paint, an image-forming material for photography, graphic arts, copier and printer use, and a photoabsorbing material for color filter use.
Common problems of these dyes to be solved include, for example, optimization of absorption wavelength and form of spectral absorption curve, an improvement of a molar absorption coefficient, and a preservability improvement including, typically, light stability or thermal stability.
For forming a full-color or three primary colors, three kinds of dyes, yellow, magenta and cyan, are required. Particularly, a cyan dye having an excellent absorption characteristic and a preservation stability has been needed.
On the other hand, with the rapid increase in information volume, a large volume optical recording medium has received much attention. In an organic optical recording medium capable of simple and high density information-recording with a relatively inexpensive semi-conductor laser, a relatively long wavelength-absorbing dye capable of absorbing rays of light from a red region to a near infrared region is used. Heretofore, among a variety of dyes, a cyanine dye excellent in both absorption and reflection characteristics has been utilized for this purpose. However, the cyanine dyes have had a shortcoming that in information data is lost in storage or record ability declines because stability such as light stability of the dye was low.
For solving the above-mentioned problems, for example, U.S. Pat. Nos. 3,432,300 and 4,050,938 and Japanese Patent Publication Open to Public Inspection (hereinafter referred to as JP OPI Publication) Nos. 60-118748/1985, 63-199248/1988 and 2-300288/1990 disclose each a light stabilizer or a light stabilizing process. However, there have not yet accomplished to obtain any satisfactory preservation stability. On the other hand, JP OPI Publication Nos. 64-44786/1989, 2-76884/1990 and 5-17701/1993 each disclose a metal chelating dye excellent in preservation stability. However, the metal chelating dyes have not been able to be applied as an optical recording medium, because their absorption wavelengths have been too long to be used.